Firefox has a limit to how many history pages it's able to store before it runs out of space to store them. When the limit is met, Firefox starts automatically deleting the oldest items to make room for new items.

You won't be able to recover your history that has already been deleted, but you can try increasing the amount of history items that Firefox can store. Try the following:

1. Type about:config in your Firefox address bar
2. Bypass the warning
3. Right click on the listed preferences
4. Select New
5. Select integer
6. Type the name places.history.expiration.max_pages
7. Set the number of pages that you want Firefox to keep in your history

This number is how many items Firefox can store, not the number of days that Firefox can store.

NOTE: Setting this value too low could cause old history items to be automatically deleted. The higher this value is set to, the more storage space Firefox will require on your computer.

When did that change? I do have old backups, is there a way I can import from those? I know my history used to go back to at least 2013 over the summer.

Also when I put in the number it says the text I enter isn't a number.

smalls102k7 said

Also when I put in the number it says the text I enter isn't a number.

Sorry. I neglected to mention that the maximum integer value that a computer can handle is 2147483647. Entering a number higher than that will give you that error message.

Current Firefox versions keep a maximum number of visited page and do not have a time limit for the history. Firefox determines automatically how many pages can be kept without affecting the performance. You can see the current value of this maximum as the value of the read-only pref places.history.expiration.transient_current_max_pages on the about:config page.

Firefox 49+ releases keep downloads for 60 days. Downloads and long URLs expire in 60 days.